1. Field of the Invention
The present invention relates generally to tape automated bonding of semiconductor devices to form semiconductor packages, and more particularly to an improved manner for forming and connecting metal tape leads to improve heat dissipation from such packages.
Tape automated bonding is a method for simultaneously connecting a plurality of bonding pads on a semiconductor device to external circuitry. The method employs a continuous metal tape usually copper or copper plated with gold, nickel, tin, or combinations thereof, having individual frames defining metal leads which are arranged in a pattern so that the inner ends of the leads may be bonded to the bonding pads while the outer ends of the leads may be bonded to a conventional lead frame or left free to be otherwise connected to the desired circuitry.
Active circuit elements, including transistors, resistors, and the like, are located in the central portion of the semiconductor device, usually referred to as the active region, while the bonding pads are peripherally located around the active region. Such peripheral location facilitates connection to the bonding pads and also avoids damage to the active regions of the device during the bonding operation required to form the inner lead bonds. The bonding may be accomplished by either thermocompression bonding or reflow techniques, where the heat and/or pressure accompanying the bonding might result in damage to any underlying circuit elements.
Heat dissipation has long been a problem with semiconductor devices, particularly with bipolar and N-MOS, devices. The problem is exacerbated by encapsulation of the devices in plastic and ceramic packages. Numerous approaches have been developed over the years to enhance thermal dissipation from such packages, including the placement of metal heat sinks within the package to provide a direct heat dissipation path from the semiconductor device to the ambient surrounding the semiconductor package. While this approach is successful in many applications, it complicates the semiconductor packaging operation and is not always necessary for marginal heat dissipation requirements.
It would thus be desirable to provide additional semiconductor packaging techniques for producing semiconductor packages having enhanced heat dissipation characteristics, where the techniques may be easily incorporated into existing semiconductor packaging methodology. In particular, it would be desirable to provide an improved method for tape automated bonding of encapsulated semiconductor devices where the metal tape leads are utilized in an effective manner to dissipate heat from the semiconductor device through the encapsulation layer.
2. Description of the Background Art
Tape automated bonding is described in U.S. Pat. Nos. 4,330,790; 4,331,740; 4,355,463; 4,466,183; and 4,470,507. Heretofore, lead frames have been specially adapted to enhance thermal dissipation from semiconductor device packages. See, for example, Japanese Pat. Nos. 53-82168 and 53-133371 wherein lead frames having flared paddle supports for heat dissipation are described.